1. Field of the Invention
This invention relates to fluid circulation pumps, and, more particularly, to high specific speed pumps having integral electric motors.
2. Description of the Prior Art
Many chemical processes utilize fluid pumps to circulate fluids, such as water and industrial chemicals, in reactors, distribution columns, kettles, water treatment plants and the like. Pumps in that type of service typically produce comparatively high flow rates at low heads and operate at relatively high specific speeds.
One conventional device for providing circulation of fluids in such installations is a shaft sealed circulator, or elbow pump, of the type shown in FIG. 1. An axial flow impeller I is positioned inside the pipe P through which the fluid is being circulated adjacent to an elbow in the pipe. Impeller I is connected to a cantilevered shaft S. Shaft S extends through pipe P and exits through the wall W of the elbow portion of the pipe P. Seals X are provided between shaft S and wall W of pipe P where the shaft exits the pipe. The shaft is rotatably connected to a motor M, often through a belt drive BD. A bearing B is provided to rotatably support shaft S. Motor M rotates shaft S, which rotates impeller I. The rotation of impeller I produces a flow in the pumped fluid.
There are several disadvantages with that type of pump installation. The seals require a considerable amount of maintenance and must be replaced often. Some chemicals have a detrimental affect on the seals and improper alignment of the shaft can cause them to deteriorate. If the seals fail, leakage may occur, which could result in toxic emissions and hazards to personnel. In some installations, the seals may have to be isolated from the pumped fluid. In addition, the mechanical components of the drive used with prior art systems require a considerable amount of maintenance. The drive shaft length is limited, thereby requiring the motor and drive to be located near the impeller. Because the shaft must exit the pipe, suitable locations for the pump are limited to those adjacent to pipe elbows.
There is a need for a circulation pump that does not require a drive shaft for rotation of the impeller and the associated seals. There also is a need for a pump that can be installed in any desired location in a length of pipe. These and other needs have been met by this invention.